Disposable centrifuge bowls have been developed for processing anticoagulated whole blood in pheresis and cell washing procedures. Prior to about 1986, commercially available disposable blood processing centrifuge bowls were of the type generally shown in FIGS. 1 or 6 of U.S. Pat. No. 4,300,717 (hereinafter "Latham bowl"), or U.S. Pat. No. 4,086,924 (hereinafter "Grenade bowl"). The overall bowl construction in each case was similar and consisted of three essential units. The first was a multi-piece feed tube and seal assembly, which enable anticoagulated whole blood and/or wash solution to be introduced to the interior of a rotating bowl body from a fixed location, and processed blood component to be removed from the bowl body and returned to a patient or donor, or stored. The second unit comprised a two-piece bowl body welded together at a peripheral seam.
The third unit was a core body usually of fairly solid construction. The core body served a number of functions. In the Latham bowl, it provides a narrow bottom fluid channel between the base of the core and the bottom of the bowl, through which fluid admitted through a central feed tube was passed to the outer periphery of the bowl body interior. In passing through this narrow channel, "impeller" vanes, formed on the bottom of the bowl, impart rotational velocity to the incoming feed fluid. With the core design shown in the Latham bowl, fluid feed is forced to pass to the outer separation region between the inner peripheral bowl body wall and the outer peripheral wall of the core. Without this core design, it would be possible for fluid admitted at the bottom of the bowl to by-pass the separation region and pass directly from the feed tube upwardly through the space between the inner core wall and the feed tube out the effluent port formed between the skirts of the seal assembly. The rigid core body was considered essential to avoid or dampen fluid wave vibrations which might occur between the rotating sterile air in the central region between the core and the feed tube and the fluid processed in the outer separation region.
The Grenade bowl construction is similar, except that the middle bowl body side walls are not tapered and the bottom of the core is not flared.
In addition to the above designs, a pheresis bowl, which was never commercialized, is described in U.S. Pat. No. 4,059,108. This bowl was of two-piece construction, formed of a lower red cell reservoir and a plasma with a core baffle system (shown in FIG. 18) for the red cell reservoir.
Sometime during 1986/87, a new centrifuge bowl became commercially available. The construction of this bowl is shown in the FIG. 4-6 embodiment of co-pending U.S. Pat. application Ser. No. 07/232,544 filed 8/15/88, which is a continuation of Ser. No. 888,764 filed 7/22/86. This new bowl differed from the prior art bowl by the use of a one-piece integral blow molded bowl body. Among other things, this construction (hereinafter "integral bowl") eliminated the need for a weld about the periphery of the bowl; a possible source of bowl failure at high centrifugal speeds.
The FIG. 4-6 embodiment of the integral bowl utilized a one-piece core body with an outer diameter is equal to or smaller than the opening into the bowl. The small core size is insufficient to enable the core to force feed fluid, entering the bottom of the bowl through the feed tube, to be diverted to the extreme outer periphery of the separation region between the core body and the bowl wall. This diversion is extremely important for cell washing procedures.
In cell washing systems, shed blood from a patient is filtered, collected and washed with saline in a disposable centrifuge bowl. Anticoagulated, filtered shed whole blood enters at the bottom center of the bowl and is separated by centrifugal forces into more dense red cells and less dense other components. The red cells fill the outermost portion of the rotating centrifuge bowl. As more shed blood enters the bowl, the red cells remain in the bowl displacing the supernatant (saline, plasma, contaminants, etc.) out of the mid-central region of the bowl. This concentrates the red blood cells in the bowl. Next, saline is directed into the bottom of the bowl, instead of shed blood. Saline, entering the Latham bowl, is directed by the lower extended skirt portion of the core to the outermost radius of the bowl and through the bed of packed red blood cells. In this way, the supernatant is diluted and displaced by the saline until a satisfactory "washout" efficiency is obtained.
The term "washout" efficiency, sometimes referred to as merely "washout", denotes the percentage of non-red blood cell fluid, i.e., plasma and saline and contaminants, originally entering the bowl and which are removed by the wash process. A 90% or greater efficiency is typically the goal of the wash process. At the end of the "wash" cycle, the contents of the bowl are red cells suspended in saline. The centrifugal washing procedure in conjunction with filtration concentrates the red blood cells and removes contaminants, such as blood clots, bone chips, fatty tissue and activates clotting factors. The patient can then be reinfused with his or her own washed red blood cells.
The FIG. 4-6 embodiment of the integral bowl body bowl of the parent application does not disclose a diverter structure, as in the Latham type bowl. Therefore, some of the saline wash solution may not be forced to travel through the packed red cells before exiting the bowl through the effluent skirts on the rotary seal. This substantially decreases the washout efficiency and, hence, the time it takes to complete a cell washing procedure. As might be expected, time is an extremely critical factor in cell washing procedures, both from the point of view of cost and patient comfort and safety.